Use of pineapple waste extract as fermentation medium for the production of biomass and cell protein from Candida utilis
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Date
2006-04
Authors
Ooi, Kuok Ing
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Abstract
The effects of agitation speed (100, 300, 500, 700 and 900 rpm) and
aeration rate (0.5, 1.0,2.0 and 3.0 Umin) on the Candida utilis biomass and cell
protein content were investigated in this study. C. uiilis inoculum of 106 cells/mL
(7.8 % v/v) was cultured in 1.5 L pineapple waste medium (3 °Srix) in a 2-L
fermentor for 30 h at 30 °e. Agitation speed and aeration rate have significant
effects on the dissolved oxygen concentration, which in turn affect the cell
growth and the cell protein content. The highest soluble cell protein content
(15.5 % w/w) and total biomass (7.8 gIL medium) were obtained from yeast
cultivation with agitation speed of 900 rpm. With the agitation speed then fixed
at the 900 rpm, the effects of aeration rate were studied and a maximum soluble
cell protein content (17.1 % w/w) and biomass (9.5 gIL media) were attained at
an aeration rate of 2.0 Umin.
Alternatively, optimum agitation speed and aeration rate for the
production of maximum cell protein by C. uti/is was determined by means of
response surface methodology (RSM). A 3-level full factorial design was
employed for experimental design and analysis of the results. Cultivations were
carried out in pineapple waste juice of 3 °Brix, 30°C for 30 h. Maximum soluble
cell protein of 18.2 % (w/w) and biomass of 8.7 gIL were obtained from the
optimum agitation speed of 775 rpm and aeration rate of 2.0 Umin. These
results are in close ,agreement with the model predictions, indicating the
reliability of the model used.
Fed-batch mode of fermentation was also studied to increase the
production of C. utilis biomass in pineapple waste media. After 30 h of batch
fermentation, sterile feed medium of pineapple waste was pumped into the
fermentor using three different feeding strategies (linear, exponential and
sigmoid) with 1-h and 2-h feeding intervals. Linear feeding strategy resulted in
the highest biomass production and with the feeding interval of 2 h, maximum
biomass (8.6 gIL) was attained after 10 h of the start of fed-batch fermentation.
A reduction of fermentation time as compared to batch fermentation increased
the biomass productivity (0.45 gIL per h).
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Keywords
Agitation speed and aeration rate have significant effects , on the dissolved oxygen concentration